1. Field of the Invention
This invention relates generally to an adaptive diesel engine controller and, more particularly, to a method and system for adaptively controlling injection timing and other parameters in a diesel engine to compensate for variations in fuel cetane number.
2. Discussion of the Related Art
Diesel engines are well known for their fuel economy advantages over spark ignition engines. Diesel engines have become a popular engine choice in passenger cars and light-duty trucks, in addition to their long-standing use in medium-duty and heavy-duty trucks. Modern diesel engines are quieter and easier to start than their predecessors, and also produce less soot and other objectionable emissions. These factors have further increased the appeal of diesel engines to the drivers of everyday vehicles like passenger cars and light trucks.
While diesel engines have gained in popularity, variations in diesel fuel type and quality have proliferated. This proliferation is due to a variety of factors—including temporary or regional petroleum shortages which necessitate the use of lower quality petroleum-based diesel fuels, and an increase in usage of biodiesel fuel and petroleum-biodiesel blends. As a result of these factors, a driver may find that the only diesel fuel available when needed has a lower or higher cetane number than that which is recommended. Variations in cetane number, which measures the ignitability of a diesel fuel, can cause problems with engine performance, efficiency, and emissions, among other undesirable effects.
A vehicle system which can adapt to variations in diesel fuel cetane number would provide a significant benefit to the vehicle owner. Not only could such a system adjust an engine's operating parameters in real time to optimize performance, efficiency, and emissions regardless of fuel cetane number, but the system could free the driver from worrying about what type of fuel can or cannot be put in the vehicle.